This invention relates generally to apparatus and methods for treating sewage water mixtures containing suspended solids to reduce the biochemical oxygen demand, BOD, and chemical oxygen demand, COD, suspended solids and bacteria content thereof and more particularly to such apparatus and methods adapted to be installed in sewage treatment plants of varying size, in boats having a marine toilet, in airplanes, trains, buses, mobile homes, travel trailers, vacation cottages, and the like wherein toilets having an operating mechanism similar to marine toilets are utilized.
The scope of this invention is not intended to be limited to portable and small scale applications as the invention is equally applicable to the treatment of large volumes of sewage water as might be encountered in apartment houses, housing developments, camping grounds, ships with large crews and the like, where the sewage producing population may be smaller than urban size.
In recent years increasing pollution of lakes and streams by sewage has created a pronounced health hazard. The problem has been accentuated by the increase in population, particularly in smaller population areas and in resort areas where sewage treatment facilities are inadequate. The rapidly expanding number of boat owners and users for recreational purposes have contributed to the pollution of lakes and streams by the attendant discharge of untreated sewage and other debris from the steadily increasing number of pleasure boats. In fact, pollution of streams and bodies of water from all sources has increased in such alarming proportions that state and federal authorities are seriously concerned with the problem and at present regulatory legislative action is being formulated by both the federal and the majority of state governments in the United States. Thus it will be seen that an urgent need exists for proper treatment of sewage water mixtures prior to discharge from municipalities, resort areas, vacation cottages, travel trailers and the like.
Various techniques have been previously proposed for the electrolytic treatment of sewage water mixtures from various sources, including boats, but none has proved entirely satisfactory for various reasons. One type of proposed treatment has been the disintegration of the contained solids matter in the sewage water and subsequent passage of the mixture through an electrolytic cell for disinfection of the water by the process of electrolysis of brine or sodium chloride solution contained in the said cell. However, after the disinfection treatment the mixture must be allowed to settle for extended time periods. The solids precipitated and flocculated by hydroxides formed during the electrolysis, after separation by settling, may either be conducted as a slurry into a body of water or may be isolated, dried and used as a fertilizer. This type of treatment, in addition to the time-consuming settling period, suffers from the disadvantages that the introduction of the slurry into the water creates pollution problems and the conversion of the solids to fertilizer involves time consuming expensive processing procedures and equipment. Another type of previously proposed apparatus for treatment of sewage water utilizes a diaphragm-type cell for electrolysis of sodium chloride solution in which chlorine is produced in the anode compartment and caustic solution and hydrogen gas produced in the cathode compartment. Since the sodium chloride solution is introduced into the anode compartment and sewage water into the cathode compartment, the latter is not exposed to chlorine gas and the alkaline cathode solution must be mixed with the chlorine-containing anolyte solution to sterilize the sewage water originally introduced to the cathode compartment. Alternately, the catholyte solution may after treatment be conducted to the anode compartment for sterilization therein. Such diaphragm-type cells require more maintenance than the diaphragm-free type cell as the diaphragms must be frequently cleaned and periodically replaced and additionally the cells have higher energy consumption than diaphragm-free cells. It is also necessary in the diaphragm-type cell to retain the sewage water in the cathode compartment until it becomes sufficiently alkaline so that precipitates may be formed from the alkaline materials contained in the sewage water to occlude the suspended solids in the sewage water for removal therefrom. Such treatment is time consuming and prevents rapid sterilization of the sewage water mixture.
The invention provides the advantages of concurrent rapid sterilization of the liquid portion and rapid separation by flotation of the solid portion of a sewage water mixture. Such advantages as hereinafter described result from exposure of the sewage water mixture to chemical agents produced in situ by electrolysis of a sewage water mixture containing sufficient alkali halide content capable of forming said chemical agents.
The term sewage water as used in this specification and claims means waste water from any source such as industrial water disposal, direct toilet discharge or any other type of disposed sewage liquids.